Alleviating mobile device overload conditions in a mobile communication system

ABSTRACT

A user equipment (UE) in a mobile communications system is operated in a manner that alleviates or avoids an overload condition in the UE. This involves operating a receiver of the UE to receive one or more data blocks via a channel. In response to a user equipment overload condition being detected, a channel quality indicator (CQI) value is reported to a serving base station, wherein the reported CQI value represents a channel quality that is lower than an actual quality of the channel. The UE is then operated in a manner that is consistent with the reported CQI value. UE overload conditions include overheating, and an inability to process received data blocks at the rate at which they are being received.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application61/031,162, filed Feb. 25, 2008; and of U.S. Provisional Application No.61/031,166, filed Feb. 25, 2008, which applications are herebyincorporated herein by reference in their entirety.

BACKGROUND

The present invention relates to mobile communications, and moreparticularly to methods and apparatuses for operating a mobile device toavoid or alleviate overload conditions in a mobile communication system.

The forthcoming Evolved-Universal Terrestrial Radio Access Network(E-UTRAN) Long Term Evolution (LTE) technology, as defined by 3GPP TR36.201, “Evolved Universal Terrestrial Radio Access (E-UTRA); Long TermEvolution (LTE) physical layer; General description” will be able tooperate over a very wide span of operating bandwidths (e.g., 1.4 MHz to20 MHz) and also carrier frequencies. Furthermore E-UTRAN systems willbe capable of operating within a large range of distances, frommicrocells (i.e., cells served by low power base stations that cover alimited area, such as a shopping center or other building accessible tothe public) up to macrocells having a range that extends up to 100 km.In order to handle the different radio conditions that may occur in thedifferent applications, multiple access in the downlink (i.e., thecommunications link from the base station to user equipment—“UE”) isachieved by Orthogonal Frequency Division Multiple Access (OFDMA)technology because it is a radio access technology that can adapt verywell to different propagation conditions. In OFDMA, the available datastream is portioned out into a number of narrowband subcarriers that aretransmitted in parallel. Because each subcarrier is narrowband it onlyexperiences flat-fading. This makes it very easy to demodulate eachsubcarrier at the receiver.

Data rates over 300 Mb/s will be supported for the largest bandwidth,and such data rates will be possible by using a Multiple-Input-MultipleOutput (MIMO) scheme in the down-link.

The possibility of higher data rates in combination with otherrequirements for more and more functionality within smaller and smallermobile devices increases the likelihood of high power consumption inthose devices and this, in turn, makes the possibility of severe heatingproblems ever more likely. Heating increases the risk for damage of thecircuits in the mobile device. Thus, there is a need to reduce the riskof overheating a mobile device.

Even if a circuit has not yet reached damaging levels of temperature,its correct operation is jeopardized as it approaches such temperatures.The temperature level at which this happens depends on the circuit andbus clocking speed and battery voltage. Hence, there is an intricatedependency between allowable temperature, battery voltage, and clockspeeds.

There are other problems associated with the higher data rates in modernmobile communication systems. The high peak data rates allow a system toexploit system capacity gains by appropriate scheduling of the differentusers. This means there will be a large difference between peak andaverage data rates for individual users. In some cases, this can lead toan inability of the user equipment to process and buffer all datareceived in the downlink (i.e., the communication link in the directionfrom a serving base station to the user equipment).

As to the problem of user equipment being unable to handle a peakdownlink data rate, conventional solutions involve scheduling onlylimited peak data rates to the user equipment. Alternatively, systemsmay rely entirely on data retransmissions in those instances in whichthe user equipment was not able to process all received data (e.g., incase of buffer overflow, exceeding signal processing power, or otherfactors limiting the capability of the user equipment to processinstantaneous data rates). But relying on retransmissions after anoverload has occurred can give rise to loss of timing in the userequipment's real time processes, which in turn creates a risk of theuser equipment going out-of-synchronization and dropping an existingcall.

Accordingly, there are a number of user equipment overload conditions(e.g., temperature overload, buffer overflow, signal processing poweroverload) associated with the higher data rates of modern mobilecommunications systems. It is therefore desirable to provide methods andapparatuses that handle these problems.

SUMMARY

It should be emphasized that the terms “comprises” and “comprising”,when used in this specification, are taken to specify the presence ofstated features, integers, steps or components; but the use of theseterms does not preclude the presence or addition of one or more otherfeatures, integers, steps, components or groups thereof.

In accordance with one aspect of the present invention, the foregoingand other objects are achieved in methods and apparatuses that controloperation of a user equipment in a mobile communications system. Thisoperation includes operating a receiver of the user equipment to receiveone or more data blocks via a channel. In response to a user equipmentoverload condition being detected, a channel quality indicator (CQI)value is reported to a serving base station, wherein the reported CQIvalue represents a channel quality that is lower than an actual qualityof the channel. The user equipment is then operated in a manner that isconsistent with the reported CQI value.

In an aspect of some embodiments, operation of the user equipmentinvolves sending negative acknowledgements (NAKs) to the serving basestation at a rate that is consistent with operation by means of achannel having a quality that corresponds to the reported CQI value,including sending one or more NAKs in response to acceptable receptionof one or more data blocks. In some of these embodiments, sending NAKsto the serving base station at the rate that is consistent withoperation by means of the channel having the quality that corresponds tothe reported CQI value is further performed in a manner such that theNAKs are distributed over time in a way that emulates a distribution ofNAKs that corresponds to the channel having the quality that correspondsto the reported CQI value. For example, the distribution of sent NAKsover time can be a random or pseudorandom distribution.

In another aspect of some embodiments, the reported CQI value isselected by determining which of a plurality of candidate CQI valueswill cause the user equipment to maintain as much functionality aspossible while at the same time alleviating or avoiding the userequipment overload condition.

In yet another aspect of some embodiments, the user equipment overloadcondition is an overheating condition.

In other alternatives, the overload condition can be a limitation inuser equipment processing capability. This limitation can be, forexample, a receiving buffer bottleneck; a transmitting bufferbottleneck; a signal processing bottleneck; or an inability to processreceived data blocks at an instantaneous downlink throughput rate. Asused herein, the term “bottleneck” denotes a part of a path having alower throughput rate than other parts that make up the path.

In another aspect of some embodiments, the overload condition can be analert that an actual overload condition will exist if the user equipmentcontinues operating in a present manner of operation. In theseembodiments, the user equipment is able to take actions to avoid theactual occurrence of the overload condition.

In yet other embodiments, methods and apparatuses operate a userequipment in a mobile communications system. Such operation includesoperating a receiver of the user equipment to receive one or more datablocks via a channel. A user equipment overload condition is detected.In response to the detected user equipment overload condition, a signalis sent to a serving base station, wherein the signal is a request forthe serving base station to reduce a downlink data throughput rate, andwherein the signal comprises a first field for indicating whether adownlink data throughput rate reduction is being requested, and a secondfield that indicates how the serving base station should respond whenthe downlink data throughput rate reduction is being requested.

In some embodiments, the second field is a channel quality indicator(CQI) field when the downlink data throughput rate reduction is notbeing requested.

In some embodiments, the second field indicates by how much the downlinkdata throughput rate should be reduced. The second field canalternatively indicate a maximum data rate value that the user equipmentis able to handle.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will be understood byreading the following detailed description in conjunction with thedrawings in which:

FIG. 1 is a flowchart of exemplary steps/processes carried out bysuitably adapted logic in a user equipment in accordance with exemplaryembodiments of the invention.

FIG. 2 is a high level block diagram of an exemplary user equipmentadapted to carry out the above-described functions.

FIG. 3 is a flowchart of exemplary steps/processes carried out bysuitably adapted logic in a user equipment in accordance with exemplaryembodiments of the invention that indirectly bring about the servingnode reducing a downlink data throughput rate.

FIG. 4 is a block diagram of an exemplary user equipment that includeselements that are particularly adapted to alleviate or avoid anoverheating condition within the user equipment.

FIG. 5 is a block diagram of an alternative embodiment of an exemplaryuser equipment that includes elements that are particularly adapted toalleviate or avoid an overheating condition within the user equipment.

FIG. 6 is a flowchart of exemplary steps/processes carried out bysuitably adapted logic in a user equipment in accordance with exemplaryalternative embodiments of the invention.

FIG. 7 is a block diagram of an exemplary user equipment being served byan eNode-B, and exemplary signaling from the user equipment to indicatean overload condition.

FIG. 8 is a block diagram of an exemplary user equipment that includeselements that are particularly adapted to alleviate or avoid a resourceutilization overload condition within the user equipment.

DETAILED DESCRIPTION

The various features of the invention will now be described withreference to the figures, in which like parts are identified with thesame reference characters.

The various aspects of the invention will now be described in greaterdetail in connection with a number of exemplary embodiments. Tofacilitate an understanding of the invention, many aspects of theinvention are described in terms of sequences of actions to be performedby elements of a computer system or other hardware capable of executingprogrammed instructions. It will be recognized that in each of theembodiments, the various actions could be performed by specializedcircuits (e.g., discrete logic gates interconnected to perform aspecialized function), by program instructions being executed by one ormore processors, or by a combination of both. Moreover, the inventioncan additionally be considered to be embodied entirely within any formof computer readable carrier, such as solid-state memory, magnetic disk,or optical disk containing an appropriate set of computer instructionsthat would cause a processor to carry out the techniques describedherein. Thus, the various aspects of the invention may be embodied inmany different forms, and all such forms are contemplated to be withinthe scope of the invention. For each of the various aspects of theinvention, any such form of embodiments may be referred to herein as“logic configured to” perform a described action, “logic adapted to”perform a described action, or alternatively as “logic that” performs adescribed action.

In order to facilitate the description of the various aspects ofembodiments consistent with the invention, the various embodiments aredescribed in the context of an LTE system. For example, the networkaccess point from which a user equipment obtains service is hereinreferred to as an “eNode-B”. However, the use of LTE terminology is notintended to limit the scope of the invention. For example, references to“eNode-B” made in the description as well as in the claims should beconstrued to include not only eNode-B's found in LTE systems, but alsoto their equivalents in other systems (e.g., a node B or other basestation).

In an aspect of embodiments consistent with the invention, a userequipment overload condition is detected and, in response thereto, oneor more actions are taken within the user equipment to either directlyor indirectly eliminate the cause of the user equipment overloadcondition. These and other aspects are described in greater detail inthe following.

FIG. 1 is a flowchart of exemplary steps/processes carried out bysuitably adapted logic 100 in a user equipment in accordance withexemplary embodiments of the invention. The user equipment operates in aconnected mode with a serving network (step 101). As a result, uplinkand downlink data and control information are exchanged between the userequipment and an eNode-B of the network. This exchange takes place inaccordance with a cellular system protocol such as, without limitation,LTE, e-HSPA, and WiMax.

At some point in time, an overload condition is detected in the userequipment (“YES” path out of decision block 103). The overload conditioncan be, for example, and overheating condition. Alternatively, theoverload condition can be an inability of the user equipment to processdata at the rate at which it is being received. In any of these cases,the overload condition can represent an existing condition within theuser equipment, or alternatively it can be an alert that an actualoverload condition will exist if the user equipment continues operatingin a present manner of operation.

In response to the detected overload condition, the user equipmentchanges its operation in a manner that results in alleviation oraversion of the overload condition. For example, the user equipment canrespond to an overheating condition by taking one or more steps that,either directly or indirectly, result in the user equipment reducing itslevel of power consumption. In another example, the user equipment canrespond to an incoming data rate that is too high by taking one or moresteps that cause the serving node to reduce the rate of datatransmission in the downlink direction.

FIG. 2 is a high level block diagram of an exemplary user equipment 200adapted to carry out the above-described functions. In this example, theuser equipment 200 includes first and second antennas 201, 203 each ofwhich is used for both transmission and reception of radio signals.Having more than one antenna allows the user equipment 200 to operate ina multiple input multiple output (MIMO) mode of operation, as is knownin the art. However, this is not essential to the invention and otherembodiments could involve only a single antenna or more than twoantennas. Also, the number of antennas is not a determining factor ofthe user equipment functionality, nor does it restrict the scope of theinvention. For example, due to cost limitations (e.g., the need forextra power amplifiers), it is often the case that a user equipment willbe designed to operate with asymmetric receiver/transmit paths (e.g.,two receive paths and only one transmit path).

Transceiver circuitry 205 in the user equipment 200 includes a receiverchain and a transmitter chain. The receiver chain comprises a front-endreceiver 207 that receives radio signals from the first and secondantennas 201, 203 and generates a baseband signal that is supplied tothe decoder 209. The decoder 209 processes the received baseband signaland generates therefrom the data conveyed by the radio signal. This datais supplied to an application within the user equipment 200 for furtherprocessing. The nature of that further processing is beyond the scope ofthe invention.

The transmitter chain comprises a coder 211 and a front-end transmitter213. Operation of the transmitter chain is essentially the reverse ofthat of the receiver chain. The coder 211 receives data from anapplication running within the user equipment 200 and formats the datain a manner that makes it suitable for transmission (e.g., by applyingforward error correction coding and interleaving). The coded data,residing on a baseband signal, is supplied to the front-end transmitter213 which converts the baseband signal into a modulated radiofrequencysignal. The power of the modulated radiofrequency is set to a desiredlevel and supplied to the first and second antennas 201, 203 fortransmission. (In embodiments utilizing only one transmit path, theoutput signal is supplied to only a single one of the first and secondantennas 201, 203.) Although, not illustrated in the figure, it will beunderstood that the user equipment 200 includes circuitry to ensure thatsignals to be transmitted do not appear on the input terminals of thefront-end receiver 207.

The various blocks within the transceiver 205 operate in accordance withcontrol signals that are generated by a control unit 215. In order tooperate as described with reference to FIG. 1, the user equipment 200also includes an overload detection unit 217 that monitors one or moreconditions within the transceiver 205 and determines whether theseconditions constitute an overload condition. The results of thisdetermination are supplied to the control unit 215 which can then takeappropriate actions. For example, as described above, if an overheatingcondition has been detected the control unit 215 can take one or moresteps to alleviate this condition, such as by limiting the maximumtransmit power or reducing the speed at which received data is processedor reducing the data rate of data to be transmitted. These actions aredescribed in greater detail in the following discussion.

Consider first an overheating condition within the user equipment.Changing the user equipment operation to eliminate the overheatingcondition can involve any one or a combination of the following actions.Overheating can be addressed by lowering the level of power consumptionwithin the user equipment and this can be accomplished in a variety ofways. One technique involves reducing the amount of power consumed by atransmitter part of the user equipment circuitry. For example, themaximum allowed transmitter power (typically 24 dBm maximum transmitterpower in an LTE or e-HSPA system) of the user equipment's transmittercan be restricted. Reduction of the maximum allowed transmitter powerresults in a typically significant lower power consumption in thetransmitter part but this in turn reduces the maximum possible uplinkdata throughput rate. In some embodiments, it is advantageous to informthe eNode-B that the user equipment will be using a reduced transmitpower level, so that the network can take this into consideration whenscheduling uplink allocation (i.e., because reduced transmit power meansthat data rates will be reduced).

Another way to reduce the power consumption, and thereby reduce thetemperature in the user equipment, is to disable one or moretransmitters when the user equipment includes more than one. This leavesonly a subset of the user equipment's transmitters enabled, and theseare used to maintain a connection with the network.

The temperature within the user equipment can also be reduced bydecreasing the power consumed by the receiver circuitry of the userequipment. A direct way of doing this is to disable one or more receiverchains, leaving only a subset of the receivers powered on in order tomaintain a connection with the network.

Another way to do this is to reduce the clock rate that governs thedecoder process. Since the power consumption in the baseband isproportional to the clock rate, a lower level of power consumption willbe achieved. However, this also results in a lower level of maximumdownlink data throughput.

Yet another technique for restricting the power consumed by the userequipment, and thereby reduce the temperature within the user equipment,is to restrict the downlink data rate. Because a significant part of thebaseband power consumption is proportional to the data rate, a reduceddata rate results in lower power consumption. Since the serving node isresponsible for setting the downlink data throughput rate, it isnecessary for the user equipment take some action that will cause theserving node to make the desired data rate adjustments.

In some embodiments, this can be accomplished by directly signaling theneed for a lower data throughput rate to the serving node. Typically,however, permissible signaling is governed by the published standardsfor the given system type. In the event that the applicable standarddoes not provide a mechanism whereby the user equipment can directlyrequest a lower downlink data throughput rate, it is still possible forthe user equipment to bring about this result. FIG. 3 is a flowchart ofexemplary steps/processes carried out by suitably adapted logic 300 in auser equipment in accordance with exemplary embodiments of the inventionthat indirectly bring about the serving node reducing a downlink datathroughput rate. In one aspect of this exemplary embodiment, the userequipment sends a channel quality indicator (CQI) report to the eNode-B(or equivalent), wherein the reported value (CQI_(REPORTED)) isintentionally set to a value that indicates a lower quality channel thenactually exists (i.e., the true channel quality value should be set toCQI_(ACTUAL)) (step 301). The theory on which this action is based is asfollows: The CQI value is typically derived from the instantaneoussignal-to-interference ratio (SIR) of the received signal. The valueCQI_(ACTUAL) is associated with the highest possible throughput rate forthe SIR of the received signal. A lower CQI value indicates to theeNode-B that the SIR is lower. As a result, the eNode-B will respond byincreasing the level of coding that is applied to the transmittedinformation. The more coding is applied, the lower the downlinkthroughput rate.

In some embodiments, this might be all that is required: By reducing theCQI value, the network will typically respond by introducing more codinginto the transmitted bits, thereby reducing the downlink throughput.

In some other embodiments, however, the network tests the validity ofthe reported CQI value. For example, the worse the channel is, the moreerrors one would expect to occur as blocks of data are transmitted fromthe serving node to the user equipment at a given code rate. At theserving node, this can be measured by, for example, measuring the numberof negative acknowledgments (NAKs) that are received during a givenperiod of time. As is well-known, a NAK is sent by a receiver of a datablock back to the sender to indicate that the block was received witherrors and should be re-sent. Accordingly, a serving node can measurethe rate at which NAKs are received from the user equipment and cancompare this with what would be expected when the CQI is as reported bythe user equipment. For example, a typical block error rate that asystem would expect to achieve is 10%. But if the network reduces thedownlink throughput data rate in response to its “belief” that theCQI_(REPORTED) value accurately represents the channel quality, which isactually better than reported, the actual NAK rate will likely be lowerthan expected. If the NAK rate is less then what would be expected forCQI_(REPORTED), then the network could assume that CQI_(REPORTED) isinaccurate and maintain (or return to) the (pre-)existing downlinkthroughput rate.

To prevent this from happening in such embodiments, the user equipmentshould be operated in a manner that is consistent with the reported CQIvalue (step 303). For example, the user equipment should send NAKs tothe serving node at a rate that is consistent with a channel whosequality corresponds to the reported CQI value. This will likely meansending one or more NAKs for blocks of data whose reception wasacceptable (i.e., received without errors or received with correctableerrors).

In some embodiments, even this may be insufficient to “convince” thenetwork that the channel between the serving node and the user equipmentreally is as poor as reported by the user equipment. In such cases,additional steps would be required. For example, for a given channelquality the network may expect not only that a certain number of NAKswill be received during a given period of time, but that these NAKs willbe distributed in an expected way over that time period. Accordingly,the user equipment in such embodiments should not only send NAKs at arate that corresponds to the reported CQI value, but should also ensurethat the distribution of these NAKs over time matches an expecteddistribution for the reported CQI value. For example, the distributionof NAKs can be made to be random or pseudorandom.

Given that reporting a lower CQI value will cause the network to lowerits downlink throughput rate, the user equipment is faced with thequestion of exactly what value to report. In some embodiments, this canbe dealt with by, for a given set of reportable values, choosing a valuethat is just less than what the actual CQI value would be.Alternatively, a user equipment could always report a lowest possibleCQI value when it wishes to reduce the downlink throughput rate.However, in many embodiments it is advantageous to select a CQI value bydetermining which of a plurality of candidate CQI values will cause theuser equipment to maintain as much functionality as possible while atthe same time extinguishing the user equipment overload condition.

In selecting a suitable CQI value to be reported, the following factorsshould be considered: In exemplary embodiments, (e.g., LTE and HSPA),each CQI incremental step represents an increment of 1 dB. A report ofCQI=0 typically represents the worst channel quality, so the eNode-B mayrespond to such a report by eliminating normal data traffic to the userequipment. (Control signaling should still be sent, however, to permitimprovements to be made by, for example, handing over the connection toanother eNode-B.) By reducing the CQI by a fixed number of steps (e.g.,reporting a CQI value that is lower than CQI_(ACTUAL) by an amountranging from 6 to 12, which would be 6-12 dB lower than the receivedSIR), the downlink throughput will be reduced by 6-12 dB (a factor of4-16), significantly reducing the risk of the user equipmentexperiencing the overload condition. To illustrate this by an example,suppose a user equipment experiences an overload condition when CQI=28and the downlink throughput rate is 25 Mb/s. Reducing by a factor of 4-8still allows a downlink throughput rate of from 2-6 Mb/s, which is stillreasonably good service for the user, and is well above the RadioResource Control (RRC) signaling needs (which are about a maximum of 100kb/s).

FIG. 4 is a block diagram of an exemplary user equipment 400 thatincludes elements that are particularly adapted to alleviate or avoid anoverheating condition within the user equipment 400. The user equipment400 includes many of the same elements as those described earlier withrespect to FIG. 2. Accordingly, those elements that are common to bothfigures need not be described again. The user equipment 400 includes atemperature sensing unit 401 that generates a signal, {circumflex over(T)}_(i), that represents an i:th estimate (wherein i is an integer) ofthe temperature within the user equipment 400. This temperature signalis supplied to a control unit 403.

The control unit 403 compares the temperature estimate with a thresholdvalue. The comparison indicates whether the user equipment 400 is in or(in some embodiments) approaching an overheating condition. In responseto the detected overheating condition, the control unit 403 generatescontrol signals to cause any one or more of the above-describedoverheating alleviating actions to be taken (e.g., limiting transmitterpower, reducing the rate of decoding, etc.).

FIG. 5 is a block diagram of an alternative embodiment of an exemplaryuser equipment 500 that includes elements that are particularly adaptedto alleviate or avoid an overheating condition within the user equipment500. The user equipment 500 includes many of the same elements as thosedescribed above with respect to FIG. 4. Accordingly, those elements thatare common to both figures need not be described again. The userequipment 500 differs from the user equipment 400 in that the thresholdlevel against which the temperature estimate is compared is not a fixedvalue, but is instead determined dynamically. To perform this function,the user equipment 500 includes a threshold determining unit 501. In theillustrated embodiment, the threshold determining unit 501 determineswhat temperature level would constitute an overheating condition (orwould indicate that the user equipment 500 is about to overheat) basedupon the present battery voltage, data buffer level, and clock speed ofprocessing units and/or buses within the user equipment 500. A strategyis adopted wherein, in order to avoid taking unnecessary actions, ahigher threshold value is used for transient effects (e.g., transmissionbursts) and/or when a temperature rise is predictable and slow (e.g.,ongoing battery use). By contrast, in order to ensure that action istaken before overheating becomes a serious problem, a lower thresholdvalue is used when the heating activity is less transient (e.g.,predictable moderate to quick heating resulting from a long termprocess) and/or when a temperature rise is relatively unpredictable(e.g., as with high data rates and/or clock speeds).

More specifically, temperature problems can originate from differentsources, each associated with its own level of predictability and rateof temperature rise. These characteristics can offer guidance about whatwould constitute a suitable threshold value. It is desirable to be ableto take action before a temperature becomes high enough to cause damageor otherwise detrimentally impact performance. Thus, situationsassociated with very fast heating call for a low threshold, so thatameliorative action can be taken as soon as possible. By contrast,situations that cause slow heating can be associated with a highthreshold level because quick action is not required—in thesecircumstances, the user equipment can be permitted to continue itshigher level of performance for some time before being degraded in somemanner to reduce power (and thereby reduce temperature). When the natureof the heating is unpredictable, prudence calls for a lower thresholdlevel so that ameliorative action can be taken sooner rather than laterto avoid any possible damage.

Whether a heat producing set of circumstances is long lasting ortransient can also be a factor when determining a suitable thresholdlevel. For example, if circumstances are known to be transient, a highthreshold level may be acceptable even if fast heating is expectedbecause that heating may not last long enough to do any harm.

Some examples will illustrate the various points. Consider a short burstof a high transmit power amplifier output power while data rates are low(e.g., as indicated by clock speed). Heating may be fast, but thesituation is known to be transient, so a higher temperature thresholdwould be appropriate for such circumstances to avoid taking unnecessaryaction. Other temperature problems arise from conditions that persistover a longer period of time, such as very high data rates. (High datarates can cause overheating because higher data rates require a higherclock speed, which in turn consumes more power than lower clock speeds.)For these overheating problems that arise slowly over time, a lowerthreshold is appropriate.

Monitoring the battery level is useful because the lower the voltage,the lower the power consumption in the chip (power is proportional tothe square of the supply voltage). Therefore, the lower the batterylevel, the longer it will take to heat up the circuitry, so thetemperature threshold value can be set to a higher value.

Monitoring the data buffer level is useful because informationindicating that the data buffer is full implies that there is a highrisk that the situation for overheating (due to high processing load)will continue for some time, whereas an indication of low data bufferutilization implies that the processing load (and hence temperature)will likely go down soon (i.e., when the buffer is empty). The formersituation calls for a lower threshold value if heating occurs quickly,whereas the latter calls for a higher threshold value in order to avoidtaking unnecessary action to address a situation that will soon fixitself.

The threshold value generated by the threshold determining unit 501 isthen supplied to a control unit 503.

The control unit 503 then compares the temperature estimate with thedynamically determined threshold value. As in the earlier-describedembodiment, the comparison indicates whether the user equipment 500 isin or (in some embodiments) approaching an overheating condition. Inresponse to the detected overheating condition, the control unit 503generates control signals to cause any one or more of theabove-described overheating alleviating actions to be taken (e.g.,limiting transmitter power, reducing the rate of decoding, etc.).

The discussion will now turn to embodiments in which the overloadcondition is an inability of the user equipment to handle data at therate at which it is being provided in the downlink direction. Asmentioned earlier, this can be attributable to a number of differentcauses, including but not limited to a receiver buffer overflow or adownlink data rate that exceeds the user equipment's signal processingpower.

FIG. 6 is a flowchart of exemplary steps/processes carried out bysuitably adapted logic 600 in a user equipment in accordance withexemplary embodiments of the invention. The user equipment operates in aconnected mode with a serving network (step 601). As a result, uplinkand downlink data and control information are exchanged between the userequipment and an eNode-B (or equivalent). This exchange takes place inaccordance with a cellular system protocol such as, without limitation,LTE, e-HSPA, and WiMax.

While connected to the network, the user equipment monitors theutilization of one or more (depending on the particular embodiment) userequipment resources (step 603). These resources include, but are notlimited to, receive buffer utilization, and signal processingutilization.

So long as no resource overload is detected (“NO” path out of decisionblock 605), operation continues as just described.

However, if a resource overload is detected (“YES” path out of decisionblock 605), the user equipment invokes logic configured to restrict thedata rate in the user equipment and network infrastructure (step 607).This involves notifying the network that it should reduce its peak datarates, either for a limited period of time or indefinitely untilotherwise notified, depending on embodiment.

In some embodiments, the user equipment signals the network to inform ofthe user equipment's limited processing capability. The signaling cantake the form of a short message that indicates, for example, thelimitation cause, the receive buffer status, the current maximumpossible data rate, the duration of the limitation and other supportinginformation. In order to limit the size of such signaling, in someembodiments there exists a preconfigured set of messages either per userequipment or per system that allows the user equipment to signal bymeans of only a message identifier. The preconfigured set of messages isknown to both the network and the user equipment. The message identifieris associated with the intended one of the preconfigured set ofmessages, so that merely communicating the message identifier issufficient to inform the network of the content of the intended message.The simplest predefined message can be one that requests an immediatehalt of downlink transmission for a specific time.

In some embodiments, a 1-bit indicator can be defined for signaling tothe network that the user equipment would like the downlink datathroughput rate to be reduced. In some embodiments, other fields can beused in conjunction with the 1-bit indicator to provide additionalinformation. For example, when the 1-bit indicator is asserted, anexisting field such as the CQI indicator can be used to indicate by howmuch the downlink data throughput rate should be reduced (i.e., the CQIindicator field indicates how the serving eNode-B should respond whenthe downlink data throughput rate reduction is being requested, andotherwise continues to represent the CQI). Alternatively, this secondfield (e.g., the CQI field) can, when the 1-bit indicator is asserted,represent the maximum value of the data rate that the user equipment isstill able to handle. FIG. 7 is a block diagram of an exemplary userequipment 701 being served by an eNode-B 703. In this illustration, theuser equipment 701 is in the process of signaling to the eNode-B 703that it would like the downlink data throughput rate to be reduced. Theexemplary signaling takes the form of a field 705 (e.g., a 1-bit field)that, when asserted, indicates the need for a data throughput ratereduction. When the data in the field 705 is asserted, anothertransmitted field (e.g., the CQI field 707) is interpreted by theeNode-B 703 as an indication of by how much the downlink data throughputrate should be reduced, or alternatively the maximum value of the datarate that the user equipment is still able to handle.

In response to the signal from the user equipment (regardless of theform of the signal), the network responds by adjusting the downlinkthroughput rate in a manner consistent with the particular messagereceived.

As mentioned above with respect to other embodiments, permissiblesignaling within a mobile communications network is typically governedby the published standard for the given system type. In the event thatthe standards do not provide a mechanism whereby the user equipment candirectly request a lower downlink data throughput rate, it is stillpossible for the user equipment to bring about this result. Inparticular, the logic 300 and steps/processes described earlier withreference to FIG. 3 are suitable for indirectly bringing about theresult that the network will reduce its downlink throughput rate. (Asused herein, the term “indirect” means that the user equipment takes oneor more actions that, within the communications standard under which theuser equipment is operating, do not directly indicate to the networkthat the user equipment is experiencing some sort of overload condition;nonetheless, the action(s) taken by the user equipment result(s) in thenetwork reducing the downlink throughput rate.) It will be recalled thatthe technique described with reference to FIG. 3 involves the userequipment sending a CQI report to the eNode-B (or equivalent), whereinthe reported value (CQI_(REPORTED)) is intentionally set to a value thatindicates a lower quality channel then actually exists (i.e., the truechannel quality value should be set to CQI_(ACTUAL)) (step 301).

Then, if required to “convince” the network that the reported CQI valuerepresents actual channel conditions, the user equipment should beoperated in a manner that is consistent with the reported CQI value(step 303). For example, the user equipment should send NAKs to theserving node at a rate (and possibly also a distribution over time) thatis consistent with a channel whose quality corresponds to the reportedCQI value. This will likely mean sending one or more NAKs for blocks ofdata whose reception was acceptable (i.e., received without errors orreceived with correctable errors).

Given that reporting a lower CQI value will cause the network to lowerits downlink throughput rate, the user equipment is faced with thequestion of exactly what value to report. In some embodiments, this canbe dealt with by, for a given set of reportable values, choosing a valuethat is just less than what the actual CQI value would be.Alternatively, a user equipment could always report a lowest possibleCQI value when it wishes to reduce the downlink throughput rate.However, in many embodiments it is advantageous to select a CQI value bydetermining which of a plurality of candidate CQI values will cause theuser equipment to maintain as much functionality as possible while atthe same time extinguishing the user equipment overload condition.

In alternative embodiments, the user equipment indirectly brings aboutthe network reducing the downlink throughput data rate by reporting NAKsinstead of positive acknowledgements (ACKs) for some data blocks whosereception was acceptable. For those data blocks that are misleadinglyreported as “not received”, the user equipment can either discard theoriginally received data block and rely on the retransmitted version, orkeep the originally transmitted version and discard the retransmittedversion. This technique allows the user equipment to regulate thereceived data rate. However, this technique has a disadvantage in thatthe network continues to send data at the high data rate, therebyneedlessly occupying the air interface.

FIG. 8 is a block diagram of an exemplary user equipment 800 thatincludes elements that are particularly adapted to alleviate or avoid aresource utilization overload condition within the user equipment 800.The user equipment 800 includes many of the same elements as thosedescribed earlier with respect to FIG. 2. Accordingly, those elementsthat are common to both figures need not be described again. The userequipment 800 includes additional elements that are adapted to carry outthe steps/processes illustrated in FIG. 6. These include a thresholddetermining unit 801 that receives one or more configuration signalsthat indicate what resources are available within the user equipment.This information can indicate such things as buffer size, signalprocessing capacity, or any other resource within the user equipmentthat has the potential to be overloaded by an excessive downlinkthroughput rate. The threshold determining unit 801 generates from thisinformation one or more threshold values that represent a level ofresource utilization that corresponds to the user equipment 800 being in(or alternatively about to enter) a resource utilization overload.

The one or more threshold levels are supplied to an overload detectionunit 803 that monitors one or more conditions within the transceiver 205and also from one or more signals that indicate present utilizationlevels of one or more resources associated with one or moreapplications, and determines from these (by means of comparison withcorresponding ones of the one or more threshold levels) whether existingconditions constitute (or will constitute) an overload condition. Theoverload detection unit 803 generates an overload status signal that issupplied to a utilization control unit 805. If the overload statussignal is asserted (meaning that an overload condition has or willoccur), the utilization control unit 805 generates control signals thatcause the user equipment to take steps to alleviate (or prevent) theoverload condition, such as those described above with reference to FIG.6. Control lines to the decoder 209 and 211 enable the utilizationcontrol unit 805 to control the respective decoding and coding rates, asappropriate. For example, some user equipment resources that are used byboth uplink and downlink processing (e.g., buffer and processing unit)can benefit from considering the operation of both reception andtransmission paths together. A control line to the front-end transmitter213 enables the output transmitter power to be adjusted, as needed.

The invention provides a number of ways that enable a user equipment toalleviate or avoid a number of different types of overload conditions.Where that overload can be alleviated by reducing the downlink datathroughput rate, a number of embodiments enable this to be achieved evenwhen a system does not provide a direct mechanism for the user equipmentto request the desired data rate reduction.

The invention has been described with reference to particularembodiments. However, it will be readily apparent to those skilled inthe art that it is possible to embody the invention in specific formsother than those of the embodiment described above.

For example, separate embodiments have been described in which, in some,temperature overload conditions are addressed, and in others, processingoverload conditions are addressed. However, in yet other alternatives, auser equipment comprises elements that enable both issues to be dealtwith. For example, some embodiments would include the equivalent of thetemperature sensing unit 401 and the threshold determining unit (bothdepicted in FIG. 5) as well as the equivalent of the thresholddetermining unit (depicted in FIG. 8). In such embodiments, controllogic can perform all of the functions attributed to the control unit503 and the utilization control unit 805 described above.

Thus, the described embodiments are merely illustrative and should notbe considered restrictive in any way. The scope of the invention isgiven by the appended claims, rather than the preceding description, andall variations and equivalents which fall within the range of the claimsare intended to be embraced therein.

1. A method of operating a user equipment in a mobile communicationssystem, the method comprising: operating a receiver of the userequipment to receive one or more data blocks via a channel; detecting auser equipment overload condition; in response to the detected userequipment overload condition, reporting a channel quality indicator(CQI) value to a serving base station, wherein the reported CQI valuerepresents a channel quality that is lower than an actual quality of thechannel; operating the user equipment in a manner that is consistentwith the reported CQI value, including sending negative acknowledgements(NAKs) to the serving base station at a rate that is consistent withoperation by means of a channel having a quality that corresponds to thereported CQI value, wherein sending NAKs to the serving base station atthe rate that is consistent with operation by means of the channelhaving the quality that corresponds to the reported CQI value is furtherperformed in a manner such that the NAKs are distributed over time in away that emulates a distribution of NAKs that corresponds to the channelhaving the quality that corresponds to the reported CQI value.
 2. Themethod of claim 1, wherein: sending negative acknowledgements (NAKs) tothe serving base station at the rate that is consistent with operationby means of the channel having the quality that corresponds to thereported CQI value includes sending one or more NAKs in response toacceptable reception of one or more data blocks.
 3. The method of claim1, wherein the distribution of sent NAKs over time is a random orpseudorandom distribution.
 4. The method of claim 1, wherein thereported CQI value is selected by determining which of a plurality ofcandidate CQI values will cause the user equipment to maintain as muchfunctionality as possible while at the same time alleviating or avoidingthe user equipment overload condition.
 5. The method of claim 1, whereinthe user equipment overload condition is an overheating condition. 6.The method of claim 1, wherein the user equipment overload condition isa limitation in user equipment processing capability.
 7. The method ofclaim 6, wherein the limitation in user equipment processing capabilityis a receiving buffer bottleneck.
 8. The method of claim 6, wherein thelimitation in user equipment processing capability is a transmittingbuffer bottleneck.
 9. The method of claim 6, wherein the limitation inuser equipment processing capability is a signal processing bottleneck.10. The method of claim 6, wherein the limitation in user equipmentprocessing capability is an inability to process received data blocks atan instantaneous downlink throughput rate.
 11. The method of claim 1,wherein the user equipment overload condition is an alert that an actualoverload condition will exist if the user equipment continues operatingin a present manner of operation.
 12. An apparatus for operating a userequipment in a mobile communications system, the apparatus comprising:logic configured to operate a receiver of the user equipment to receiveone or more data blocks via a channel; logic configured to detect a userequipment overload condition; logic configured to report a channelquality indicator (CQI) value to a serving base station in response tothe detected user equipment overload condition, wherein the reported CQIvalue represents a channel quality that is lower than an actual qualityof the channel; logic configured to operate the user equipment in amanner that is consistent with the reported CQI value, including sendingnegative acknowledgements (NAKs) to the serving base station at a ratethat is consistent with operation by means of a channel having a qualitythat corresponds to the reported CQI value, wherein the logic configuredto send NAKs to the serving base station at the rate that is consistentwith operation by means of the channel having the quality thatcorresponds to the reported CQI value operates in a manner such that theNAKs are distributed over time in a way that emulates a distribution ofNAKs that corresponds to the channel having the quality that correspondsto the reported CQI value.
 13. The apparatus of claim 12, wherein: thelogic configured to send negative acknowledgements (NAKs) to the servingbase station at the rate that is consistent with operation by means ofthe channel having the quality that corresponds to the reported CQIvalue includes logic configured to send one or more NAKs in response toacceptable reception of one or more data blocks.
 14. The apparatus ofclaim 12, wherein the distribution of sent NAKs over time is a random orpseudorandom distribution.
 15. The apparatus of claim 12, wherein thelogic configured to report the CQI value to the serving base station inresponse to the detected user equipment overload condition selects thereported CQI value by determining which of a plurality of candidate CQIvalues will cause the user equipment to maintain as much functionalityas possible while at the same time alleviating or avoiding the userequipment overload condition.
 16. The apparatus of claim 12, wherein theuser equipment overload condition is an overheating condition.
 17. Theapparatus of claim 12, wherein the user equipment overload condition isa limitation in user equipment processing capability.
 18. The apparatusof claim 17, wherein the limitation in user equipment processingcapability is a receiving buffer bottleneck.
 19. The apparatus of claim17, wherein the limitation in user equipment processing capability is atransmitting buffer bottleneck.
 20. The apparatus of claim 17, whereinthe limitation in user equipment processing capability is a signalprocessing bottleneck.
 21. The apparatus of claim 17, wherein thelimitation in user equipment processing capability is an inability toprocess received data blocks at an instantaneous downlink throughputrate.
 22. The apparatus of claim 12, wherein the user equipment overloadcondition is an alert that an actual overload condition will exist ifthe user equipment continues operating in a present manner of operation.